Heat exchanger in refrigeration system



July 2, 1957 w. J. DONOVAN 2,797,554

HEAT EXCHANGER m REFRIGERATION SYSTEM Filed Jan. 6, 1954 2 Sheets-Sheet1 I INVENTOR 3 l WZZZLam-[Donovan I ATT EYs y 1957 w. J DONOVAN2,797,554

HEAT EXCHANGER IN REFRIGERATION SYSTEM Filed Jan. 6, 1954. 2Sheets-Sheet 2 E; I I OR 51 William JDonovan ATTORN 5 4.

I-EAT EXCHANGER IN REFRIGERATION SYSTEM William J. Donovan, WestHartford, Conn.

Application January 6, 1954, Serial No. 402,447

7' Claims. (Cl. 62-11755) This invention relates to refrigerationsystems and components of the type used therein, and more in particularto improved heat-interchange equipment and operation, illustratively, sothat the gas refrigerant flowing from the evaporator is passed intoheat-interchange relationship with the liquid refrigerant flowing to theevaporator.

An object of this invention is to provide for the improved operation ofrefrigeration systems. A further object is to provide improvedheat-interchange apparatus. Another object is to provide a unit forpassing liquid refrigerant in heat interchange relationship with gasrefrigerant without the difliculties which have been encountered withprior equpment for accomplishing the same purposes. A further object isto provide for the above with a structure which is light in weight andsturdy, and which is efficient in operation. These and other objectswill be in part obvious and in part pointed out below.

In the drawings:

Figure l is a view showing. the heat interchange unit in perspective,but representing the remainder of the system schematically; v

Figure 2 is an enlarged sectional view on the line 22 of Figure 1;

Figure 3 is a fragmentary view with parts broken away of one of theindividual heat-interchange assemblies of the unit of Figure 2;

Figure 4 is a sectional view on the line 44 of Figure 3; and,

Figure 5 is a sectional view on the line 5--5 of Figure 2.

Referring to Figure I of the drawings, a low temperature refrigerationsystem is represented schematically and in somewhat simplified form,with a motor-compressor 2, a condenser 4, a receiver 6,. a heatinterchange unit 8, an evaporator 10, interconnecting refrigerant lines,and controls. pressed in condenser 2 and condensed in condenser 4, andthe liquid refrigerant flows to receiver 6. From receiver 6 the liquidrefrigerant passes to the liquid inlet connection 12 of unit 8 andpasses through this unit and out through the liquid outlet connection 14and through an expansion valve 16 to the evaporator 10. The gaseousrefrigerant with accompanying oil flows to the gas inlet connection 18of unit 8, and through the unit and out through the gas outletconnection 20 from which it returns to the compressor.

Unit 8 is formed by a cylindrical steel shell 22 having the connectionsreferred to above, and no other openings. Referring to Figures 2 and 5,shell 22 encloses twentyseven individual tube assemblies 24. which arerigidly mounted at their ends (Figure 5) in a pair of end: plates orpartitions 26 and 28. These partitions are welded to the surroundingwall of shell 22, and each of the tubes extends through each of theplates and is welded thereto. Hence, the partitions divide the spacewithin the shell into a right-hand header 30, a left-hand header 32, anda central space 34 which is mainly occupied? by the tubes 24.

Each ofthe tube assemblies 24 is formed of an outer tube 36 and anenclosed cylindrical'fin' assembly=38. The fin assembly is shown best inFigure 3 and 4 and comprises a fin structure 42 wound around a centraltube 40. The fin structure 42 comprises a series of substantially'flatradial finportions 44 and 46 interconnected at theinner Duringoperation, the refrigerant is co.

nited States Patent" surface of tube 36 by bends 48 and interconnectedat the outer surface of tube 40 by bends 50. During manufacture, the finstructure is formed by bending or corrugating a flat strip of sheetmetal thus to form a strip which is corrugated by an angle to its sideedges. This corrugated strip is wound around tube 40, and the strip andtube are inserted into the outer tube 36. The inner tube 40 is thenexpanded so as to place the fin structure under radial compression andthis insures high heat conductivity between the entire fin assembly andthe outer tube 36. The inner U-bends 50 on the fin structure are ofsmaller radius than the U-hends 48 and this provides alternatepassageways 52" and 54 between the fin elements which differ incross-sectional configuration, but which are of similar fluid-carryingcapacity.

Referring now again to Figure 5, each of the tubes 36 has its ends 56and 58 extending beyond the ends of the enclosed fin assembly. Each ofthese tube ends has a cylindrical end portion 60 which is ofsubstantially lesser diameter than the diameter of the central portion62 of the tube. The end portions 60 are connected to the central portion62 of the tube by tapered portions 64. The end of each of the centraltubes 40 (at the left in- Figure 5) is closed at 66 by pinching the end'of the tube together after the tube assembly has been completed. Thisprevents the fluid from flowing through the central passageway in eachtube 40 so that the flow is only in the annular passageway occupied bythe fin structure 42. This insures a rapidflow of the fluid and thefluid is distributed between the various passageways-52 and 54. r Theproper distribution of the fluid is insured by the reduced diameter ends58 and 56 of the tube 36.

The refrigerant gas entering header 30 from inlet connection 18 tends todistribute itself evenly as it flows to the left into the tube ends 60.At the left of these tube ends, the gradual increasing diameter permitsthe fluid to flow radially outwardly in an evenly distributed annularstream into the ends of passageways 52 and 54. This flow is promoted bythe stoppage of flow through the central tube 40 and yet there is nomechanical obstructionto the flow which would tend to causeeddy'currents and cavitation.

of the central tube 40, and the fluid then forms into a cylindricalstream and passes into header 32' from which it is discharged throughoutlet connection 20. The flow" through the tube assemblies is at asubstantial velocity and yet the resistance to flow is not excessive.more, oil which accompanies the refrigerant gas is not trapped and itdoes not form in films upon the heat transfer surfaces.

it has been indicated above that the liquid refrigerant enters the tubeshell 22' through the liquid inlet connection 12 and it flows from theshell at the bottom through the liquid outlet connection 14. As shownbest in Figure 2, the central portions 62 of the tubes 36 aresubstantially in contact with each other, but the cylindrical shape ofthe tubes provides longitudinal passageways 68, 70 and 72 of somewhatregular patterns through which the liquid flows along the tubeassemblies. of the tube assemblies the reduced diameter tube ends 6i)provide liquid headers or header zones 72 and 76 (see- Figure 5). Hence,the liquid entering at 12 to the header zone 74 flows freely around thetube ends 60 and distributes itself evenly with. minimum resistance toflow.

It then enters the pasageways 68, 70 and 72 and flows in somewhat thinstreams and at an even rate along the tube assemblies to the right handheader zone 76 to the outlet 14.

The central space 34 Within the shell is formed by the inlet header zoneat the left,.the longitudinal passageways 68, 70 and 72, and'theright-hand outlet header zone 76.

At the left-hand end of the fin assembly the fluid flows a somewhatannular passageway at the end F urther-- However, at the ends Thecylindrical confining wall of shell 22 and the, tapered portions of thetubes 64 insure against pockets, eddy cur rents and cavitation, andthere is a smooth even flow with minimum resistance and flash gas doesnot appear. It is thus seen that the liquid is cooled and the gas isheated in an eificient and dependable manner. The substantial finsurfaces along which the gas flows, and the creation of thin evenstreams of gas flowing at a rapid rate, insures good heat conductivitybetween the gas and the fin structures. It has been indicated above thatthe fin structures are in good heat-conductive relationship with theirtubes 36 and the liquid on the outer surface of the tubes picks up theheat in an efficient manner.

The manner of fabricating the fin and tube assemblies has been discussedsomewhat above and reference may be had to theco-pending application toCecil Boling, Serial No. 310,820, filed September 22, 1952, where thereis a further disclosure. After the fin assembly and its central tube 40have been properly positioned in the outer tube and the central tube hasbeen expanded, the end of the central tube is pinched together. The endsof the tube 36 are spun to form the reduced ends 60 and the taperedportions 64. The tubes are then assembled within the end plates 26 and28 and each tube end is brazed to its end plate. This entire tube andend plate assembly is placed into the central cylindrical portion 78 ofshell 22 and end bells 80 and 82 are welded in place as shown. Theliquid inlet and outlet connections 12 and 14 are also welded in placeat this time.

I claim:

1. In refrigeration apparatus, a heat interchanger which comprises, ashell construction having a central chamber and a pair of headerspositioned adjacent thereto, partition means separating said headersfrom said central chamber, a plurality of tube assemblies each rigidlymounted on said partition means with its respective ends opening intosaid headers whereby each tube assembly provides a passageway betweensaid headers, each of said tube assemblies having its central portioncontacting the corresponding portions of a plurality of the other tubeassemblies thus to form cooperating walls of fluid passageways extendinglongitudinally along the outer surfaces of said tube assemblies, each ofsaid tube assemblies having ends of reduced cross-section and spacedfrom the respective ends of the adjacent tube assemblies whereby aheader zone is provided in said shell at each end of said tubeassemblies, each of said tube assemblies including an internal finassembly which provides for a heat interchange relationship between onefluid passing through said tube assemblies and another fluid passingthrough said central chamber in said shell externally of said tubeassemblies, means to deliver a gas to one of said headers and towithdraw the gas from the other of said headers, and means to deliver aliquid to one of said header zones at one end of said central chamber insaid shell and to withdraw a liquid from the other of said header zones.

2. In a refrigeration system which includes a compressor and a condenserand an evaporator, a heat interchanger having a central chamberconnected in the system between said condenser and said evaporator andhaving a pair of gas headers connected in said system between saidevaporator and said compressor comprising, a cylindrical shell havingsaid gas headers at its opposite ends and having said chamber positionedbetween said headers, a pair of partitions dividing said central chamberfrom said gas headers, and a plurality of tube assemblies extendinglongitudinally of said shell and each rigidly mounted at its respectiveends in said partitions with each tube end opening into one of said gasheaders whereby the gas circuit is provided through said tube assembliesbetween said gas headers, each of said tube assemblies having its endsof reduced cross-section whereby there is substantially more spacewithin said shell and outside of said tube assemblies adjacent saidpartitions than there is in the central portions of said tube assemblieswhereby header zones are provided within said central chamber adjacentsaid partitions, fluid inlet and outlet connections to said shell atsaid header zones formed by the reduced ends of said tubes at oppositeends of said chamber, each of said tube assemblies including a finassembly positioned in its central portion between said ends to increasethe heat interchange relationship.

3. In a refrigeration system having separate paths of flow for arefrigerant, a heat interchange unit connected in said separate paths offlow comprising, a cylindrical shell, 21 pair of partitions mountedsubstantially in the ends of said shell, a pair of end bellspositionedrespectively at the ends of said shell and providing headers,and a plurality of tube assemblies extending longitudinal of said shelland mounted by their ends respectively in said partitions with each tubeopen at its ends to said headers and providing a fluid passagewaybetween said headers, each of said tube'assemblies having ends of lessercross-section than its central portion and said central portionscooperating to provide longitudinal passageways along said tubeassemblies between a pair of header zones formed respectively adjacentsaid partitions by the space between the ends of said tube assemblies,and fluid inlet and outlet connections to said shell at said headerzones formed by the reduced ends of said tubes whereby to provide auniform flow in thin streams over a large surface area at the exteriorof the. tubes.

4. Apparatus as described in claim 3 wherein each of said tubeassemblies contacts a plurality of other tube assemblies substantiallythroughout its length except at said ends.

5. A heat interchange unit as described in claim 4 wherein each of saidtube assemblies comprises a sheet metal fin structure at the centralportions formed by substantially radially extending fin elementsinterconnected by U-bends, and a central element presenting acylindrical surface and holding said fin elements in radial compression.

6. A heat interchange unit as described in claim 5 wherein said centralelement comprises a metal tube, and means closing said tube to flow offluid therethrough.

7. In a refrigeration system having a compressor, a condenser and anevaporator connected in a refrigerating circuit, the combination withsaid system of a heat exchanger in said refrigerating circuit havingseparate countercurrent paths of flow for refrigerant flowing from thecondenser to the evaporator and from the evaporator to the compressorcomprising, a closed shell, a pair of transverse partitions adjacent therespective ends, and tubes extending between said partitions to provideone path of flow through said tubes, each of said tubes having anintermediate portion and end portions of reduced diameter extending fromthe intermediate portions outwardly to said partitions, saidintermediate portions of said tubes contacting at least one adjacenttube tangentially to provide restricted passages therebetween, saidshell having inlet and outlet openings at said reduced end portions ofsaid tubes adjacent the opposite ends thereof and together with therestricted passages between the intermediate portions of the tubesproviding the other path of flow.

References Cited in the file of this patent UNITED STATES PATENTS2,059,992 Gould Nov. 3, 1936 2,102,723 Kotzebue Dec. 21, 1937 2,135,235Hurford et al. Nov. 1, 1938 2,267,695 Graham Dec. 23, 1941 2,385,667Webber Sept. 25, 1945 2,413,360 Maguire et al Dec. 31, 1946 2,417,661Rosales Mar. 18, 1947 2,445,471 Buckholdt July 20, 1948 2,658,358 BolingNov. 10, 1953

